CCAS 3381 AUTOMOTIVE SKILL I

1
CCAS 3381 AUTOMOTIVE SKILL I

• SUSPENSION
• STEERING SYSTEM

2
OBJECTIVES

• To understand the operational principles and
  basic mechanisms of suspension steering systems

Double-wishbone suspension on Honda Accord 2005
Coupe
Lecture 1 hour Workshop 1 hour
3
SUSPENSION SYSTEM (1)

• Power of a car is useless if car cannot be
  controlled
• Car suspension
• maximizes friction between tires and road surface
• provide steering stability with good handling
• ensure the comfort of the passengers

4
SUSPENSION SYSTEM (2)

• Vehicle dynamics
• Ride - car's ability to smooth out bumpy road
• Handling - car's ability to safely accelerate,
  brake corner
• Road isolation - allow vehicle body to ride
  undisturbed while traveling over rough roads
• Road holding - keep tires in contact with ground
  (friction between tires and road affects a
  vehicle's ability to steer, brake accelerate)
• Cornering - minimize body roll

5
SUSPENSION SYSTEM (3)

• Frame - structural, load-carrying component
  supporting car's engine body (supported by
  suspension )
• Suspension system - setup supporting weight,
  absorbing dampening shock helps maintaining
  tire contact

• Steering system - mechanism enabling driver to
  guide direct vehicle
• Tires wheels - components making vehicle motion
  possible by way of grip /or friction with road

6
SUSPENSION SYSTEM (4)

• Springs
• Coil springs
• Leaf spring
• Torsion bars
• Air springs
• Sprung mass unsprung mass

7
SUSPENSION SYSTEM (5)

• Sprung mass - mass of the vehicle supported on
  the springs
• Unsprung mass - mass between the road and the
  suspension springs
• Stiffness of springs affects how sprung mass
  responds while the car is being driven
• Loosely sprung cars versus tightly sprung cars -
  balance passenger comfort with handling is a
  complex task

8
SUSPENSION SYSTEM (6)

• Shock absorbers - controls unwanted spring motion
  through dampening
• compression cycle
• extension cycle

9
SUSPENSION SYSTEM (7)

• Struts and Anti-sway Bars
• Strut shock absorber inside a coil spring
• provide dampening function
• provide structural support for the vehicle
  suspension
• critical safety feature - worn shocks struts
  allow excessive sway reducing tire grip, handling
  braking performance
• Anti-sway or anti-roll bars
• give moving stability
• creates a more level ride reduces vehicle sway

Common strut design
Anti-sway bars
10
SUSPENSION SYSTEM (8)

• Dependent front suspension - rigid front axle
  connecting the front wheels
• Independent system - front wheels are allowed to
  move independently (MacPherson strut, double
  wishbone)

Double-wishbone suspension on Honda Accord 2005
Coupe

• Double-wishbone allows for more control over
  camber angle of the wheel (degree to which the
  wheels tilt in and out) they also help minimize
  roll or sway and provide for a more consistent
  steering feel.

11
SUSPENSION SYSTEM (9)

• Dependent rear suspension - solid axle connects
  the rear wheels
• Independent rear suspension system both rear
  wheels are mounted sprung individually

Bose Suspension Front Module
12
SUSPENSION SYSTEM (10)
13
SUSPENSION SYSTEM (11)
14
STEERING SYSTEM (1)

• During turning your front wheels are not pointing
  in the same direction
• Geometry of steering linkage makes the inside
  wheel turn more than the outside wheel

15
STEERING SYSTEM (2)

• Rack-and-pinion steering
• most common
• converts steering wheel rotation to linear
• provides gear reduction to turn wheels
• A steering wheel rotates 360o causing wheels
  turning 20o has steering ratio of 360/ 20 181
• Variable-ratio steering
• Power Rack-and-pinion

16
STEERING SYSTEM (3)

• Recirculating-ball steering
• Used on many trucks and SUVs today
• contains a worm gear
• Power steering in a recirculating-ball system
  works similarly to a rack-and-pinion system

17
STEERING SYSTEM (4)

• Power Steering
• Rotary-vane pump driven by car's engine via a
  belt and pulley - amount of flow provided by the
  pump depends on the car's engine speed
  (pressure-relief valve)
• Rotary valvesenses steering wheel force assist
  driver only when necessary like during parking

18
STEERING SYSTEM (5)

• Todays steering system runs constantly, pumping
  fluid all the time (wastes)
• "drive-by-wire" system (like joysticks)
• General Motors concept car (Hy-wire)

19
STEERING SYSTEM (6)
20
WHAT COULD GO WRONG (1)

• Worn loose ball joints causing suspension noise
  (typically a "clunking" sound when hitting a
  bump)
• Bent wheel (shimmy on steering wheel sideway
  movement of wheel)
• Leaked shock absorbers (realignment after strut
  change)
• Shocks too soft
• Worn shocks (sway, dip, bounce)
• Loose steering wheel (gt 0.25) tie rod ends,
  rack, wheel bearing)
• Power steering morning sickness worn steering
  rack

21
WHAT COULD GO WRONG (2)

• Steering wheel jerks to one side upon hitting
  bump misalignment in chassis bent steering
  arm
• Car pulled to one side wheel misalignment
  (camber, toe-in), tire pressure, mismatched
  tires, sagging spring, dragging brake, unreleased
  parking brake, uneven load)
• Unbalanced tires static dynamic
• Most problems affecting the suspension and
  steering system develop gradually as a result of
  wear. Watch for the following warning signs.

22
WHAT COULD GO WRONG (3)

• Theres too much play (free movement) in the
  steering wheel. With power steering, there should
  be virtually no play in the wheel. In a manual
  system, there should be no more than 2 inches of
  play.
• The steering wheel vibrates or is difficult to
  turn.
• The front end of the car wobbles or shimmies.
• The car bumps as you turn the wheel while driving
  on a smooth road.

23
WHAT COULD GO WRONG (4)

• The car pulls to one side as you drive.
• The car bounces too much after hitting a bump.
• Tread wear on the front tires is uneven.

24
THE END
IQ EQ SQ TQ